Positron Emission Tomography
PET scans coupled position-emitting radionuclide tracers to other molecules, such as glucose, ammonia, or water. The radionuclide tracers simultaneously emit two high-energy photons in opposite directions that can be simultaneously detected (referred to as coincidence detection) by a PET scanner, which comprises multiple stationary detectors that encircle the region of interest.
A variety of tracers are used for PET scanning, including oxygen 15, nitrogen 13, carbon 11, and fluorine 18. The radiotracer most commonly used in oncology imaging has been fluorine 18, coupled with fluorodeoxyglucose (FDG), which has a metabolism related to glucose metabolism. While FDG has traditionally been used in cancer imaging, it potentially has many other applications.
Positron emission tomography (PET) using 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) may be considered medically necessary in:
1. The assessment of select individuals with epileptic seizures who are candidates for surgery
a. In patients with epileptic seizures, appropriate candidates are patients with complex partial seizures who have failed to respond to medical therapy and have been advised to have a resection of a suspected epileptogenic focus located in a region of the brain accessible to surgery.
2. The diagnosis of chronic osteomyelitis
The use of FDG-PET for all other miscellaneous indications is investigational, including, but not limited to:
A PET scan involves 3 separate activities: (1) manufacture of the radiopharmaceutical, which may be manufactured on site or at a regional center with delivery to the institution performing PET; (2) actual performance of the PET scan; and (3) interpretation of the results
American Academy of Neurology
Evidence-based practice parameters from the American Academy of Neurology are summarized below.
Practice Parameters on Diagnosis of Dementia
|Practice Parameter||Date||PET Recommendation|
|Diagnosis of dementia||2004: reaffirmed||PET imaging not recommended for routine use in diagnostic evaluation of dementia (LOR: moderate clinical certainty)|
|Early detection of dementia||2003: reaffirmed||Not addressed|
|Diagnosis of new-onset PD||2006: reaffirmed
2013; retired 2016
|Evidence insufficient to support or refute FDG-PET as a means of distinguishing PD from other parkinsonian syndromes|
|Evaluation of depression, psychosis, and dementia in PD||2006; retired 2018||Not addressed|
|Mild cognitive impairment||2001; 2017; 2018||Not addressed|
FDG: fluorine 18 fluorodeoxyglucose; LOR: level of recommendation; PD: Parkinson disease; PET: positron emission tomography.
American Academy of Orthopaedic Surgeons
The American Academy of Orthopaedic Surgeons (2010) published evidence-based, consensus guidelines. Fluorine 18 fluorodeoxyglucose positron emission tomography (FDG-PET) was considered:
“an option in individuals in whom diagnosis of periprosthetic joint infection has not been established and are not scheduled for reoperation. (Strength of recommendation: limited [quality of the supporting evidence is unconvincing, or well-conducted studies show little clear advantage of one approach over another])”
American College of Radiology
Evidence- and consensus-based appropriateness criteria from the American College of Radiology are summarized below.
Appropriateness Criteria for Miscellaneous Indications of FDG-PET/CT
|Appropriateness Criteria||Last Reviewed||FDG-PET/CT Criteria|
|Suspected osteomyelitis, septic arthritis, or soft tissue infection (excluding spine and diabetic foot)||2017||
|Diagnosis of dementia||2001, reaffirmed 2004||PET imaging not recommended for routine use in diagnostic evaluation of dementia (LOR: moderate clinical certainty)|
|Early detection of dementia||2001, reaffirmed 2003, 2015||Not addressed|
|Diagnosis of new onset-PD||2006: reaffirmed 2013; retired 2016||Evidence insufficient to support or refute FDG-PET as a means of distinguishing PD from other parkinsonian syndromes|
|Evaluation of depression, psychosis, and dementia in PD||2006||Not addressed|
|Dementia and movement disorders||2016||May be appropriate in individuals with possible or probable AD and to differentiate suspected FTD, LBD, CJD, or vascular dementia; usually not appropriate in individuals with suspected HD, clinical features of PD or hemochromatosis, or motoneuron disease|
|Imaging after total knee arthroplasty||2017||Usually not appropriate for routine follow-up of asymptomatic individual, in work-up for suspected periprosthetic infection, or for evaluation of prosthetic loosening|
|Seizures and epilepsy||2014||Usually appropriate for surgical planning in medically refractory epilepsy; may be appropriate for new-onset seizure unrelated to trauma in adults (age ≥18 y) and for posttraumatic (subacute or chronic), new-onset seizure; otherwise, usually not appropriate for new-onset seizure|
|Crohn disease||2014||Usually not appropriate|
|Fever without source – child||2015||May be appropriate. This procedure should not be used as the initial study. Consider if extensive clinical and imaging work-up is negative.|
|Suspected osteomyelitis of the foot in individuals with DM||2012; revised 2019||Usually not appropriatefor initial imaging. May be appropriate for soft-tissue swelling with or without ulcer, suspected osteomyelitis or early neuropathic arthropathy changes of the foot in individuals with DM, suspected osteomyelitis of the foot in individuals with DM with or without neuropathic arthropathy, and additional imaging following radiographs.|
AD: Alzheimer disease; CJD: Creutzfeldt-Jakob disease; CT: computed tomography; DM: diabetes mellitus; FDG: fluorine 18 fluorodeoxyglucose; FTD: frontotemporal dementia; HD: Huntington disease; LBD: Lewy body disease; LOR: level of recommendation; PD: Parkinson disease; PET: positron emission tomography.
Infectious Diseases Society of America
The Infectious Diseases Society of America (IDSA; 2015) published evidence-based, consensus guidelines on the diagnosis and treatment of native vertebral osteomyelitis in adults. The guidelines stated that PET “is highly sensitive for detecting chronic osteomyelitis. A negative PET scan excludes the diagnosis of osteomyelitis, including native vertebral osteomyelitis, as the sensitivity of the test is expected to be very high in view of the high concentration of red marrow in the axial skeleton.”
The IDSA (2013) published evidence-based, consensus guidelines on the diagnosis and management of prosthetic joint infections. The guidelines concluded that PET should not be routinely used to diagnose prosthetic joint infection (strength of recommendation: B [based on moderate evidence]; quality of evidence: III [expert opinion and descriptive studies]).
The IDSA (2012) published evidence-based, consensus guidelines on the diagnosis and treatment of diabetic foot infections. The guidelines concluded that the role of FDG-PET in evaluating a diabetic foot infection has not been established.
The IDSA (2018) will be publishing guidelines on the diagnosis and management of bone and joint infections in children.